Word: orbiters
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Wispy Hydrogen. Tugged by the gravity of a passing star, chunks of the Oort debris are occasionally pulled into orbits closer to the sun. Then perturbed further by the gravity of a massive planet, probably Saturn or Jupiter, they often enter a highly elliptical orbit that swings them close to the sun and then so far out again that they do not return to the vicinity of the sun for years. Some, like Encke's comet, which makes a pass around the sun every 3.3 years, have relatively small orbits. Others loop out billions of miles from...
...Biela's comet that Luboš Kohoutek made his great discovery. Interested in the minor bodies of the solar system since boyhood meteor-and comet-hunting expeditions in the Czechoslovak mountains, he had in the fall of 1971 located a cluster of about 50 small asteroids in an orbit roughly comparable to that of Biela's comet. Last February, using Hamburg Observatory's 32-in. Schmidt telescope, he tried to "recapture" the asteroids, which he feels may be the remaining chunks of the lost comet. To Kohoutek's surprise, he not only obtained pictures...
...ordinary visitor from distant space. After making some rush observations of his own ("We spent a very tense weekend out at Harvard Observatory's Agassiz Station"), he reported that the comet Kohoutek had been sighted at a distance of roughly 480 million miles from earth, barely within the orbit of Jupiter. (Halley's comet, by contrast, was not found on its last approach until it was some 180 million miles closer to earth-even though astronomers knew where to look for it.) Never before had a comet been detected at such a great distance...
...miles in diameter, far larger than most comets, probably including Halley's. Other astronomers calculate that Kohoutek weighs about 1 trillion tons. But size is not Kohoutek's only distinction. It will pass within 13 million miles of the sun. That close flyby, well within the orbit of Mercury, should make for a dazzling interaction between sun and comet. Perhaps most important of all, astronomers describe it as a "dirty" comet, one with an outer layer of dust that has probably never been stripped off by solar heating. That layer may prevent the comet from becoming as bright...
Last week four unmanned Soviet spacecraft were about halfway along on a journey to Mars. When they arrive in February and March, two of the ships are expected to make soft landings while the other two remain in orbit around the Red Planet. Meanwhile, the U.S.'s Mariner 10 spacecraft was well on its way to Venus on the initial lap of the first two-planet, photo-reconnaissance flight. After Mariner has swept by Venus in February, using the braking force of that planet's gravity to change course, it will pass next March within 621 miles...